1. Field of the Invention
This invention relates to apparatus and methods for efficiently invalidating metadata for target count-key-data (CKD) volumes.
2. Background of the Invention
When establishing and withdrawing CKD FlashCopy® relationships, the data tracks of the target CKD volume must have their metadata invalidated. This is because the customer data on the target CKD volume is no longer valid or is unknown. The invalidation must occur before the data tracks on the CKD volume are accessed.
When establishing a FlashCopy® relationship, the metadata may be replicated from the source CKD volume to the target CKD volume. However, this is typically not performed due to the time constraints of copying the metadata. Instead, the target metadata is invalidated and rebuilt at the time a data track is copied from the source volume to the target volume. That is, when a data track is copied from the source volume to the target volume, the metadata for the data track is rebuilt on the target side.
Currently, a FlashCopy® target bitmap is used to determine which data tracks need to have their metadata invalidated. If a data track has not yet been copied to a target volume, during track access a FlashCopy® intercept code will indicate that the metadata must be invalidated for this track. Although this optimization maintains the space efficiency for the target volume, it is insufficient for FlashCopy® relationships between extent-space-efficient (ESE) volumes since the target bitmap may not be set for all data tracks in the target volume.
When processing a FlashCopy® withdraw command, the metadata for the target volume must also be invalidated. Since the FlashCopy® relationship will be removed by the withdraw command, the processing cannot be performed asynchronously as occurs with a FlashCopy® establish command. The processing can be slow and can cause command timeouts when the target volume is very large.
In view of the foregoing, what are needed are apparatus and methods to more efficiently invalidate metadata associated with CKD target volumes when point-in-time-copy relationships, such as FlashCopy® relationships, are established or withdrawn. Ideally, such apparatus and methods will more efficiently invalidate metadata associated with target extent-space-efficient (ESE) volumes.